1. Field of the Invention
The present invention relates to electronic components, and in more detail, to an electronic component that is mounted using terminals and ground electrodes located on one main surface of a substrate.
2. Description of the Related Art
Electronic components such as switch modules and wireless LAN modules mounted in cellular phones have a plurality of terminals, to be connected to a mounting board, formed in a predetermined pattern.
For example, as illustrated in an arrangement diagram of FIG. 9, a relatively large ground electrode 112a is formed in the center of the bottom surface of a high-frequency module 101 and relatively small signal terminals 110, bias terminals 111, and ground terminals 112b are formed in the peripheral portion. In addition, a signal terminal 110 and a bias terminal 111 are formed within a ground electrode 112a. 
By forming terminals and ground terminals in this manner, signal terminals and bias terminals can be formed at positions of a layered substrate under the mounted components, whereby wiring using unnecessary inner layer circuit patterns is not required and deterioration of insertion loss and interference with other patterns are prevented. Further, since there are no restrictions on terminal arrangement, a reduction in the size of a module is realized (refer to Japanese Unexamined Patent Application Publication No. 2005-277075, for example).
Referring to FIG. 9, an opening is formed in the lower ground electrode and a signal electrode and a bias electrode are formed within the opening, but an opening is not formed in the upper ground electrode. Hence, although terminals are arranged with left-right symmetry, i.e., with line symmetry about a center line in the up-down direction, the terminals are not symmetrically arranged about a center line in the left-right direction.
All the terminals, i.e., signal terminals, bias terminals, and ground terminals, are used for connection to a mounting board. Hence, in the configuration in which a signal terminal and a bias terminal are arranged within the opening of the lower ground electrode, mounting strength is reduced in certain places due to an imbalance in the amount of solder. This may cause generation of mounting defects or variations in the electric characteristics due to an unstable ground potential.